Supported osmates, process for preparation thereof, and a process for the preparation of chiral vicinal diols using supported osmate catalyst

ABSTRACT

The present invention provides a supported osmate useful as a reusable catalyst in the preparation of vicinal diols. The present invention also relates to a process for the preparation of supported osmates of the formula (S—NR 3 ) 2 OsO 4 .nH 2 O wherein S is a support, R is an alkyl group, n is the number of water molecules and use thereof in the preparation of vicinal diols by asymmetric dihydroxylation (AD) of olefins in presence of cinchona alkaloid compounds.

RELATED APPLICATIONS

This is a division of our earlier application 10/096,071 filed Mar. 132002, now U.S. Pat No. 6,646,168 which is a continuation in part ofapplication Ser. No. 09/983,231 filed Oct. 23, 2001 (now U.S. Pat. No.6,552,234 B1). This application is also related to our prior co-pendingapplication Ser. No. 10/366,611 filed Feb. 14, 2003 as a division ofapplication Ser. No. 09/983,231.

FIELD OF THE INVENTION

The present invention relates to a supported osmate useful as a reusablecatalyst in the preparation of vicinal diols. The present invention alsorelates to a process for the preparation of supported osmates of theformula (S—NR₃)₂OsO₄.nH₂O wherein S is a support, R is an alkyl group, nis the number of water molecules and use thereof in the preparation ofvicinal diols by asymmetric dihydroxylation (AD) of olefins in presenceof cinchona alkaloid compounds.

BACKGROUND OF THE INVENTION

Asymmetric dihydroxylation of olefins in the presence of cinchonaalkaloid results in products that are important intermediates in thepreparation of various drugs and chemicals. For example, the products ofcinnamic acid esters are intermediates for taxol side chain, ananticancer drug, diltiazem, calcium antagonist and chloramphenicol, anantibiotic. Proranolol, a β blocker can also be derived from diolsobtained through this method.

There are serious disadvantages in performing the catalytic AD reactionwith homogeneous system in the manufacture of vicinal diols due topresence of toxic remnants of osmium in products and high cost of osmiumtetraoxide or potassium osmate dihydrate. By employing the heterogeneouscatalytic system, the cost naturally comes down due to easy recovery ofthe catalyst and very insignificant loss of osmium tetraoxide, whencompared with homogeneous system. The products thus obtained usingheterogeneous catalyst system are benign in the sense that the presenceof osmium in minor impurities in the dihydroxylated products is alsoprecluded.

U.S. Pat. Nos. 4,871,855 and 5,260,421 disclose processes for asymmetricdihydroxylation of olefins using osmium tetraoxide and cinchonaalkaloids using homogenous catalyst systems. These processes involvecumbersome recovery of the osmium catalyst from the reaction mixture,generation of toxic waste and the potential presence of toxic osmium inthe product.

U.S. Pat. Nos. 5,516,929 and 5,260,461 disclose asymmetricdihydroxylation of olefins using osmium tetraoxide and polymer boundcinchona alkaloids in a heterogeneous system. The quantitative recoveryof the toxic osmium catalyst, lower enantioselectivity and reduction inactivity and enantioselectivity in each recycle experiments are some ofthe disadvantages associated with this process.

U.S. Pat. No. 5,968,867 discloses asymmetric dihydroxylation of olefinsusing osmium tetraoxide and silica gel supported bis-cinchona alkaloidderivatives in a heterogeneous system. Quantitative recovery of toxicosmium catalyst is difficult and a reduction in activity andenantioselectivity of the catalyst is observed in each and every recycleexperiment.

European Patent 940,170 A2 describes the catalytic asymmetricdihydroxylation of alkenes using a polymer supported osmium catalyst.The drawbacks of this process are that higher amounts of catalyst arerequired (5 mol %), the reaction time is very long and expensivepolymers are used as supports.

OBJECTS OF THE INVENTION

The main object of the invention is to provide a heterogeneousrecyclable supported osmate of the general formula (S—NR₃)₂OsO₄.nH₂Owherein S is a support, R is an alkyl group, n is the number of watermolecules and use thereof in the preparation of vicinal diols byasymmetric dihydroxylation (AD) of olefins in presence of cinchonaalkaloid compounds.

It is another object of the invention to provide a process for thepreparation of a novel heterogeneous recyclable supported osmate of thegeneral formula (S—NR₃)₂OsO₄.nH₂O wherein S is a support, R is an alkylgroup, n is the number of water molecules and use thereof in thepreparation of vicinal diols.

It is another object of the invention to provide a environmentallyfriendly process for the asymmetric dihydroxylation of olefins to obtainvicinal diols using a novel heterogeneous supported osmate of theinvention.

It is a further object of the invention to provide a process for thepreparation of vicinal diols with good enantioselectivity, activity andyield by the asymmetric dihydroxylation of olefins using a novel osmatecatalyst of the invention.

It is yet another object of the invention to provide a process for thepreparation of vicinal diols by the asymmetric dihydroxylation ofolefins in the presence of cinchona alkaloids and derivatives thereof,which process is simple, economical and results in a product with notraces of toxic osmium therein.

It is a further object of the invention to provide a process for thepreparation of vicinal diols by the asymmetric dihydroxylation ofolefins in the presence of cinchona alkaloids and derivatives thereofwherein the catalyst is capable of recycle several times withoutsubstantial loss of activity or in yield of product.

SUMMARY OF THE INVENTION

These and other objects of the invention are achieved by using the novelsupported heterogeneous osmate catalyst of the general formulaS—NR₃)₂OsO₄.nH₂O wherein S is a support, R is an alkyl group, n is thenumber of water molecules for the asymmetric dihydroxylation of olefinsin the presence of cinchona alkaloids to obtain vicinal diols with goodyield and selectivity.

The novelty of the invention lies in the supported osmate catalyst andin preparation of vicinal diols in presence of cinchona alkaloids orderivatives employing oxidants.

Accordingly, the present invention provides a supported osmate of thegeneral formula S—NR₃)₂OsO₄.nH₂O wherein S is a support, R is an alkylgroup, n is the number of water molecules.

In one embodiment of the invention, the support is selected from resinand silica.

In another embodiment of the invention, R is selected from methyl,ethyl, propyl, butyl and like alkyl groups.

In a further embodiment of the invention, the osmium content in thecatalyst is in the range of 1 to 30%.

In a further embodiment of the invention, the support S as synthesizedhas charge balancing anions selected from chloride, bromide, iodide,fluoride, hydroxide and acetate.

The invention also relates to a process for the preparation of a novelheterogeneous supported osmate catalyst of the formula S—NR₃)₂OsO₄.nH₂Owherein S is a support, R is an alkyl group, n is the number of watermolecules, said process comprising reacting potassium osmate with aquaternary ammonium species in water.

In one embodiment of the invention, the potassium osmate is of theformula K₂OsO₄2H₂O.

In another embodiment of the invention, the quaternary ammonium speciesis of the formula S—NR₃X wherein S is a support, R is alkyl and X isselected from Cl, Br, I, F, —OH and OAc.

In a further embodiment of the invention, the reaction is carried out ata temperature in the range of 25 to 100° C. for a period in the range of5-24 hours.

In one embodiment of the invention, the osmium content in the catalystis in the range of 1 to 30%.

In another embodiment of the invention, the support S is selected fromresin and silica.

In a further embodiment of the invention, the support S as synthesizedhas charge balancing anions selected from chloride, bromide, iodide,fluoride, hydroxide and acetate.

In another embodiment of the invention, R is selected from methyl,ethyl, propyl, butyl and like alkyl groups.

The present invention also provides a process for the preparation ofvicinal diols comprising asymmetrically dihydroxylating thecorresponding olefin in the presence of a cinchona alkaloid using anoxidant in a solvent selected from the group consisting of water,acetone, acetonitrile, t-butanol and any mixture thereof, at atemperature in the range of −70 to 100° C. for a period in the range of0.5 to 24 hours, and in the presence of a catalytic amount of aheterogeneous supported osmate catalyst of the general formulaS—NR₃)₂OsO₄.nH₂O wherein S is a support, R is an alkyl group, n is thenumber of water molecules, and recovering the pure vicinal diol.

In one embodiment of the invention, the osmium content in the catalystis in the range of 1 to 30%.

In another embodiment of the invention, the support S is selected fromresin and silica.

In a further embodiment of the invention, the support S used has chargebalancing anions selected from chloride, bromide, iodide, fluoride,hydroxide and acetate.

In another embodiment of the invention, R is selected from methyl,ethyl, propyl, butyl and like alkyl groups.

In yet another embodiment of the invention, the amount of supportedosmate used in the reaction is 0.01 to 10 mol % of osmium content withrespect to the substrate.

In yet another embodiment of the invention the solvent used comprises asolvent system selected from the group consisting of water:acetone,water:acetonitrile and water:t-butanol, the ratio of water to acetone,acetonitrile and t-butanol being in the range of 1:1 to 1:3, andwater:acetone:acetonitrile in a ratio of 1:1:1.

In another embodiment of the invention, the catalyst is recovered fromthe reaction system and recycled to the reaction system as many times asdesired.

In a further embodiment of the invention, the oxidant used is selectedfrom the group consisting of N-methylmorpholine N-oxide (NMO),trimethylamine N-oxide, hydrogen peroxide, t-butyl hydrogen peroxide,potassium ferricyanide, sodium periodate and molecular oxygen.

In yet another embodiment of the invention, the cinchona alkaloid andderivatives thereof comprise a monomeric and polymeric chiral ligand.

In a further embodiment of the invention, the chiral ligand is selectedfrom the group consisting of (DHQD)₂PHAL, (DHQD)₂PYR, (DHQD)₂AQN,DHQD-OAc, DHQD-CLB, DHQD-PHN, DHQD-MEQ, DHQD-IND and pseudoenantiomericforms thereof.

DETAILED DESCRIPTION OF THE INVENTION

The novelty of the invention lies in the supported osmate catalyst andin preparation of vicinal diols in the presence of cinchona alkaloids orderivatives employing oxidants.

The novel supported osmate is of the general formula (S—NR₃)₂OsO₄.nH₂Owherein S is a support, R is an alkyl group, n is the number of watermolecules. The support is preferably selected from resin or silica R ispreferably selected from methyl, ethyl, propyl, butyl and like alkylgroups. The osmium content in the catalyst is generally in the range of1 to 30%. The support S as synthesized may contain charge balancinganions selected from chloride, bromide, iodide, fluoride, hydroxide andacetate.

The heterogeneous osmate catalyst of the general formula(S—NR₃)₂OsO₄.nH₂O wherein S is a support, R is an alkyl group, n is thenumber of water molecules is prepared by reacting potassium osmate withsupported quaternary ammonium species in water as a solvent at atemperature in the range of 25 to 100° C. for a period in the range of5-24 hours to obtain the desired catalyst.

The process for preparation of vicinal diols comprises asymmetricallydihydroxylating the corresponding olefin in the presence of a cinchonaalkaloid compound using an oxidant in a solvent selected from the groupconsisting of water, acetone, acetonitrile, t-butanol and any mixturethereof at a temperature in the range of −70 to 100° C. for a period inthe range of 0.5 to 24 hours, and in the presence of a catalytic amountof a heterogeneous supported osmate catalyst of the general formula(S—NR₃)₂OsO₄.nH₂O wherein S is a support, R is an alkyl group, n is thenumber of water molecules, and recovering the pure vicinal diol by anyconventional method. The amount of supported osmate used in the reactionis 0.01 to 10 mol % of osmium content with respect to the substrate.

The catalyst can be recovered from the reaction system by anyconventional process and recycled to the reaction system several timeswithout any substantial loss of activity or of yield of the product. Theoxidant used is selected from N-methylmorpholine N-oxide (NMO),trimethylamine N-oxide, hydrogen peroxide, t-butyl hydrogen peroxide,potassium ferricyanide, sodium periodate and molecular oxygen. Thecinchona alkaloid and derivatives thereof comprise a monomeric andpolymeric chiral ligand such as for example (DHQD)₂PHAL, (DHQD)₂PYR,(DHQD)₂AQN, DHQD-OAc, DHQD-CLB, DHQD-PHN, DHQD-MEQ, DHQD-IND andpseudoenantiomeric forms thereof.

Scientific Explanation

In the present invention, novel supported osmates were prepared for thefirst time using the anion exchange method from the supported quaternaryammonium species. The osmate anions present on the support areresponsible for the dihydroxylation activity of the reaction. Theactivity of the supported osmate is similar or higher than thehomogeneous counterparts. Without wishing to be bound by any theory, itis believed that the higher activity is ascribed to the support effect.The large positive potential of OsO₄ ²⁻ support surface inducespolarisation of N→O bond and facilitates oxygen transfer.

Higher yields and enantioselectivities are obtained with supportedosmate catalysts used in the asymmetric dihydroxylation of olefins inaqueous organic solvents. Since the dihydroxylated products areimportant intermediates for the preparation of drugs andpharmaceuticals, this invention is timely and appropriate. Therefore,supported osmate is a better option for the synthesis of vicinol diols.The supported osmate catalysts prepared from various supports offeredgood yields and enantioselectivies in presence of cinchona alkaloids.Thus this invention offers the best techno-economic route for thesynthesis of vicinol diols, intermediates for the preparation of drugsand pharmaceuticals.

Supported osmates are prepared as exemplified and used in catalyticamounts for preparing vicinol diols by asymmetric dihydroxylation ofolefins employing oxidants in presence of cinchona alkaloid compounds ina heterogeneous manner as described.

The following examples are given by way of illustration of the presentinvention and therefore should not be construed to limit the scope ofthe invention.

Preparation of Catalysts EXAMPLE 1

Resin-OsO₄: Resin was obtained by quaternization of triethylamine (2.1mL, 21 mmol) with 1 g of chloromethylated styrene-divinylbenzenecopolymer (Merrifield resin, capacity-2.1 mequiv/g) in chloroform (20mL) under reflux for 24 h. 1 g of quaternary ammonium resin wassuspended in 100 mL of 0.8 mmol aqueous potassium osmate solution andstirred at 25° C. for 12 h under nitrogen atmosphere. The solid catalystwas filtered, washed thoroughly with 300 mL of water and vacuum dried toobtain Resin-OsO₄ (0.641 mmol of Os per g).

EXAMPLE 2

SiO₂—OsO₄: Modified silica was obtained by quaternisation oftriethylamine (0.7 mL, 7 mmol) with bromopropylsilica (capacity 0.7mequiv/g) in chloroform (20 mL) under reflux for 24 h. 1 g of quaternaryammonium silica was suspended in 100 mL of 0.33 mmol aqueous potassiumosmate solution and stirred at 25° C. for 12 h under nitrogenatmosphere. The solid catalyst was filtered, washed thoroughly with 300mL of water and vacuum dried to obtain SiO₂—OsO₄ (0.317 mmol of Os perg).

Asymmetric Dihydroxylation of Olefins

The asymmetric dihydroxylation reaction of olefins was performed usingthe following method in order to evaluate supported osmates of thepresent invention.

Supported osmate (0.01 eq. wt. of osmium content), bis-cinchona alkaloid(DHQD)₂PHAL (0.01 Eq. Wt.) and N-methylmorpholine-N-oxide (1.5 Eq. Wt.)were stirred in the mixed solvent of water/acetone/acetonitrile (in thevolume ratio of 1:1:1). To this mixture was added an olefin (1.0 Eq. Wt)slowly for a period of 12 h. After the reaction, the supported osmatecatalyst was filtered off and washed with ethyl acetate. The combinedfiltrates were concentrated under reduced pressure. The chiral ligandwas recovered from the aqueous layer after acidification (1N HCl). Theconcentrated organic layer was purified to afford the correspondingcis-diol by using conventional processes. The yield and the opticalpurity of the product were determined.

Catalytic Asymmetric Dihydroxylation of Olefins UsingN-Methylmorpholine-N-Oxide as a Co-Oxidant EXAMPLE 3

Catalytic Asymmetric Dihydroxylation Reaction of Trans-Stilbene by UsingResin-OsO₄:

Resin-OsO₄(0.01 eq wt), Hydroquinidine 1,4-phthalazinediyl diether(DHQD)₂PHAL (0.01 eq. wt.) and N-methylmorpholine-N-oxide (1.5 eq. wt.)were stirred in mixed solvent of water/acetone/acetonitrile (volumeratio of 1:1:1). To this mixture trans-stilbene (1.0 eq. wt) was addedand stirred at room temperature for 6 hours. After the reaction,supported osmate catalyst was filtered off and washed with methanol.Combined filtrates were concentrated under reduced pressure. Chiralligand was recovered from aqueous layer after acidification (1N HCl).Pure product was obtained by removing solvent at reduced pressurefollowed by column chromatography.

(R,R)-(+)-1,2-diphenyl-1,2-ethandiol of more than 99.0% of enantiomericexcess was obtained (yield 96%)

[∝]_(D)+92.44 (c 1.0, EtOH): e.e.=99.4%

Catalyst Reusability Experiments EXAMPLE 4

Catalytic asymmetric dihydroxylation reaction of trans-stilbene by usingResin-OsO₄ which had been used in Example 3 without further addition ofosmate catalyst.

The reaction was performed using identical process as in Example 3.(R,R)-(+)-1,2-diphenyl-1,2-ethandiol of more than 99.0% of enantiomericexcess was obtained (yield 95%) [∝]_(D)+92.90 (c 1.0, EtOH): e.e.=99.9%

EXAMPLE 5

Catalytic asymmetric dihydroxylation reaction of trans stilbene by usingResin-OsO₄ which had been used in Example 4 without further addition ofsupported osmate catalyst.

The reaction was performed by using an identical process as in Example3. (R,R)-(+)-1,2-diphenyl-1,2-ethandiol of more than 99.0% ofenantiomeric excess was obtained (yield 97%)

[∝]_(D)+92.16 (c 1.0, EtOH): e.e.=99.1%

EXAMPLE 6

Catalytic asymmetric dihydroxylation reaction of trans-stilbene by usingResin-OsO₄ which had been used in Example 5 without further addition ofsupported osmate catalyst.

The reaction was performed by using identical process as in Example 3.(R,R)-(+)-1,2-diphenyl-1,2-ethandiol of more than 99.0% of enantiomericexcess was obtained (yield 94%)

[∝]_(D)+92.25 (c 1.0, EtOH): e.e.=99.2%

EXAMPLE 7

Catalytic asymmetric dihydroxylation reaction of trans-stilbene by usingResin-OsO₄ which had been used in Example 6 without further addition ofSupported osmate catalyst.

The reaction was performed by using an identical process as in Example3. (R,R)-(+)-1,2-diphenyl-1,2-ethandiol of more than 99.0% ofenantiomeric excess was obtained (yield 96%)

[∝]_(D)+92.81 (c 1.0, EtOH): e.e.=99.8%

EXAMPLE 8

Catalytic asymmetric dihydroxylation reaction of trans-stilbene by usingResin-OsO₄ which had been used in Example 7 without further addition ofsupported osmate catalyst.

The reaction was performed by using an identical process as in Example3. (R,R)-(+)-1,2-diphenyl-1,2-ethandiol of more than 99.0% ofenantiomeric excess was obtained (yield 98%)

[∝]_(D)+92.25 (c 1.0, EtOH): e.e.=99.2%

EXAMPLE 9

Catalytic asymmetric dihydroxylation reaction of trans-stilbene bySiO₂-OsO₄

The reaction was performed by using an identical process as in Example3. (R,R)-(+)-1,2-diphenyl-1,2-ethandiol of more than 99.0% ofenantiomeric excess was obtained (yield 97%)

[∝]_(D)+92.34 (c 1.0, EtOH): e.e.=99.3%

EXAMPLE 10

Catalytic asymmetric dihydroxylation reaction of styrene by usingResin-OsO₄

The reaction was performed by using an identical process as in Example 3except slow addition of olefin with a reaction time of 12 hours.(R)-phenyl-1,2-ethanediol of more than 95.0% of enantiomeric excess wasobtained (yield 94%) [α]_(D) −34.29 (c 1.32, EtOH): e.e.=95.7%

EXAMPLE 11

Catalytic asymmetric dihydroxylation reaction of trans-beta-methylstyrene by using Resin-OsO₄

The reaction was performed by using an identical process as in Example 3except slow addition of olefin with a reaction time of 12 hours.(R,R)-1-phenyl-1,2-propanediol of more than 98.0% of enantiomeric excesswas obtained (yield 97%)

[∝]_(D) −30.50 (c 1.32, EtOH): e.e.=98.1%

EXAMPLE 12

Catalytic asymmetric dihydroxylation reaction of methyl trans-cinnamateby using Resin-OsO₄.

The reaction was performed by using an identical process as in Example 3except slow addition of olefin with a reaction time of 12 hours.(2S,3R)-2,3-dihydroxy-3-phenylpropionate of more than 99% ofenantiomeric excess was obtained (yield 96%)

[≢]_(D) −10.6 (c 1.0, CHCl₃): e.e.=99%

EXAMPLE 13

Catalytic asymmetric dihydroxylation reaction of allyl 1-naphthyl etherby using Resin-OsO₄

The reaction was performed by using an identical process as in Example 3except slow addition of olefin with a reaction time of 12 hours.2,3-dihydroxypropyl-1-naphthyl ether of more than 77.0% of enantiomericexcess was obtained (yield 94%)

[∝]_(D) +5.18 (c 1.0, CH₃OH): e.e.=77.4%

EXAMPLE 14

Catalytic dihydroxylation reaction of trans-stilbene by usingResin-OsO₄:

Resin-OsO₄ (0.01 Eq. Wt.), N-methylmorpholine-N-oxide (1.5 Eq. Wt.) andtrans-stilbene (1.0 Eq. Wt) in the mixed solvent ofwater/acetone/acetonitrile (in the volume ratio of 1:1:1) were stirredat room temperature for 6 hours. After completion of the reaction, thecatalyst was filtered off and washed with ethyl acetate. Combinedfiltrates were concentrated under reduced pressure. The pure product,1,2-diphenyl-1,2-ethandiol was obtained by removing the solvent reducedpressure followed by column chromatography. (yield 93%).

The experimental results in the Examples 3 to 14 are tabulated in Tables1 and 2.

TABLE 1 Reuse of Resin-OsO₄ for asymmetric dihydroxylation reaction oftrans-stilbene Ex.No run Yield ee 3 1 96 99.4 4 2 95 99.9 5 3 97 99.1 64 94 99.2 7 5 96 99.8 8 6 98 99.2

TABLE 2 Catalytic asymmetric dihydroxylation reaction of olefins byusing Resin-OsO₄ Ex.No Catalyst^(a) Ligand Olefin Time Yield^(b) ee^(c)Config.^(d)  9 SiO₂—OsO₄ (DHQD)₂PHAL Trans-stilbene 6 97 99.3 RR 10Resin-OsO₄ (DHQD)₂PHAL Styrene 12 94 95.7 R 11 Resin-OsO₄ (DHQD)₂PHALE-Methylstyrene 12 97 98.1 RR 12 Resin-OsO₄ (DHQD)₂PHAL E- 12 96 99.02S, 3R Methylcinnamate 13 Resin-OsO₄ (DHQD)₂PHAL Allyl 1-naphrhyl 12 9477.4 S ether 14 Resin-OsO₄ — Trans-stilbene 6 93 — — ^(a)Equivalentweight ratio of the reactants = olefin: osmium: cinchona alkaloid =1:0.01:0.01, reaction temperature 25° C. ^(b)Yield percent after theseparation by using column chromatography. ^(c)% e.e.(e.e. meansenantiomeic excess) was determined by HPLC analysis using chiral columns^(d)absolute configuration was compared with the [α]_(D) values in theliterature.

Solvent effects:

EXAMPLE 15

Catalytic asymmetric dihydroxylation reaction of trans-stilbene byResin-OsO₄:

The reaction was performed by an identical process as in Example 3except the solvent is water/acetone (in the volume ratio of 1:3).(R,R)-(+)-1,2-diphenyl-1,2-ethandiol of more than 99.0% of enantiomericexcess was obtained (yield 95%)

[∝]_(D) +91.90 (c 1.0, EtOH): e.e.=99.0%

EXAMPLE 16

Catalytic asymmetric dihydroxylation reaction of trans-stilbene byResin-OsO₄:

The reaction was performed by an identical process as in Example 3except the solvent is water/acetonitrile (in the volume ratio of 1:3).(R,R)-(+)-1,2-diphenyl-1,2-ethandiol of more than 99.0% of enantiomericexcess was obtained (yield 93%)

[α]_(D) +91.1 (C 1.0, EtOH): e.e.=99.0%

EXAMPLE 17

Catalytic asymmetric dihydroxylation reaction of trans-stilbene byResin-OsO₄:

The reaction was performed by an identical process as in Example 3except the solvent is water/t-butanol (volume ratio of 1:3) and thereaction time is 24 h (R,R)-(+)-1,2-diphenyl-1,2-ethandiol of more than99.0% of enantiomeric excess was obtained (yield 91%)

[∝]_(D) +91.6 (c 1.0, EtOH): e.e.=99.0%

EXAMPLE 18

Catalytic asymmetric dihydroxylation reaction of trans-stilbene byResin-OsO₄:

The reaction was performed by an identical process as in Example 3except the solvent is water/t-butanol (volume ratio of 1:2) and thereaction time is 24 h (R,R)-(+)-1,2-diphenyl-1,2-ethandiol of more than99.0% of enantiomeric excess was obtained (yield 90%)

[∝]_(D) +92.1 (c 1.0, EtOH): e.e.=99.0%

EXAMPLE 19

Catalytic asymmetric dihydroxylation reaction of trans-stilbene byResin-OsO₄:

The reaction was performed by an identical process as in Example 3except the solvent is water/t-butanol (volume ratio of 1:1) and thereaction time is 36 h (R,R)-(+)-1,2-diphenyl-1,2-ethandiol of more than99.0% of enantiomeric excess was obtained (yield 92%)

[∝]_(D) +92.3 (c 1.0, EtOH): e.e.=99.0%

TABLE 3 Solvent effects in catalytic asymmetric dihydroxylation reactionof trans-stilbene by Resin-OsO₄ Ex. No Catalyst^(a) Ligand Olefin TimeYield^(b) ee^(c) Config.^(d) 15 Resin-OsO₄ (DHQD)₂PHAL Trans-stilbene 695 99 RR 16 Resin-OsO₄ (DHQD)₂PHAL Trans-stilbene 6 93 99 RR 17Resin-OsO₄ (DHQD)₂PHAL Trans-stilbene 24 91 99 RR 18 Resin-OsO₄(DHQD)₂PHAL Trans-stilbene 24 90 99 RR 19 Resin-OsO₄ (DHQD)₂PHALTrans-stilbene 36 92 99 RR

The main advantages of the present invention are:

1. A novel and ecofriendly process for asymmetric dihydroxylation ofolefins is presented.

2. The present process dispenses the use of soluble, toxic osmiumtetraoxide or potassium osmate dihydrate instead heterogeneous reusablesupported osmates are used.

3. Supported osmates are prepared and used for asymmetricdihydroxylation of olefins as heterogeneous catalysts. The use ofheterogeneous supported osmates precludes the presence of osmium intraces with product.

4. The enantioselectivity and the yields are good.

5. The work-up procedure is simple.

6. The catalyst is subjected to many recycles, which displayedconsistent activity.

7. The present process is environmentally safe since there is nodisposal problem.

8. The process is economical

We claim:
 1. A process for the preparation of a novel heterogeneoussupported osmate catalyst of the formula (S—NR₃)₂OsO₄.nH₂O wherein S isa support, R is an alkyl group, n is the number of water molecules, saidprocess comprising reacting potassium osmate with a quaternary ammoniumspecies in water.
 2. A process as claimed in claim 1 wherein thepotassium osmate is of the formula K₂OsO₄2H₂O.
 3. A process as claimedin claim 1 wherein the quaternary ammonium species is of the formulaS—NR₃X wherein S is a support, R is a alkyl, and X is selected from Cl,Br, I, F, —OH and OAc.
 4. A process as claimed in claim 1 wherein thereaction is carried out at a temperature in the range of 25 to 100° C.for a period in the range of 5-24 hours.
 5. A process as claimed inclaim 1 wherein the osmium content in the catalyst is in the range of 1to 30%.
 6. A process as claimed in claim 1 wherein the support S isselected from resin and silica.
 7. A process as claimed in claim 1wherein the support S as synthesized has charge balancing anionsselected from chloride, bromide, iodide, fluoride, hydroxide andacetate.
 8. A process as claimed in claim 1 wherein is R is alkylselected from methyl, ethyl, propyl and butyl groups.